Transformer



June 3, 1941. AM|LL| 2,244,386

' TRANSFORMER Filed lay 20, 19:59

Fig. 2.

A Inventor A Guglielmo Camilli b5 Hi5 Attorney.

Patented June 3, 1941 TRANSFORMER Guglielmo Camilli, Pittsfield, Mass, assignor to General Electric Company, a corporation of New York Application May 20, 1939, Serial No. 274,763

6 Claims.

My invention relates to transformers. The general object of the invention is to provide an improved transformer structure which may be 'used simultaneously both as a potential trans- I3 is connected between one of the conductive layers I6 and. a ground connection I8. This primary winding I3 surrounds both part I and II permeability of the core, however, should be as Y high as possible for maximum accuracy. The permeability increases with increasing flux density to some maximum value, depending upon the particular material used in the core, and then decreases if the flux density is further increased. The ordinary silicon steel commonly used in current transformer cores has a maximum permeability when the flux density is something like 16,000 lines per square inch. Another object of the invention is to provide an improved transformer arrangement which may be operated as a current transformer with high core flux density but without corresponding loss in accuracy as a result of high magnetizing current.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 is a diagrammatic, sectional view of a transformer constructed and arranged in accordance with the invention and applied as a bushing transformer, and Fig. 2 is an explanatory, diagrammatic view of a magnetic core and windings arranged and connected in accordance with the invention.

The transformer shown in Fig. 1 includes a magnetic core formed in two parts I0 and I I provided with two primary windings I2 and I3 and two secondary windings i4 and I5. The primary winding I2 is shown diagrammatically in Fig. 1 as the conductor of a condenser type bushing provided with cylindrical, conductive layers I6 which form a series of condensers and which assume potentials determined by the capacities between the layers. The secondary winding I4 surrounds the magnetic core I0 and H just as in the conventional current transformer and may be connected to an instrument I! such as an ammeter for indicating the current in the primary conductor or winding I2. The primary winding of the magnetic core, but it surrounds them differentially with respect to the primary winding I2 so that the voltages induced in the two parts of, the winding I3 by the winding I2 are equal and opposed and therefore so that no resultant voltage between the terminals of the winding I3 is induced by the winding I2. The secondary winding I5 also surrounds both parts In and Ii of the magnetic core differentially with respect to the primary winding I2 so that no resultant voltage is induced by the primary winding I2 between the terminals of the secondary winding I5. The secondary winding I5, however, will obviously cooperate with the primary winding I3 and these two windings I3 and I5 with the two parts III and Ii of the core will operate as a potential transformer so that the secondary winding I5 may be connected to a voltmeter or other voltagedevice IS. The primary windings I2 and I3 are both connected to the same source of primary current and the winding I3 is preferably proportioned to induce a magnetic flux in both parts I0 and II of the core correspondin". to the maximum permeability of the particular magnetic material used in the core. This permits the primary winding I2 and the secondary winding I I to operate as a current transformer with maximum permeability in the core but without any losses due to the magnetizing current. If the magnetic core I0 and II is formed with the usual high quality silicon steel commonly used in the cores of current transformers, the core will operate at maximum permeability with the primary winding I3 proportioned to induce a magnetic flux of something like 16,000 lines per square inch, but this flux density may of course be varied with different magnetic materials and any increase of flux density provided by the primary potential winding I3 will of course increase the permeability of the core and the accuracy of the current ratio between the currents in the primary winding I2 and the secondary current winding I4.

The arrangement of the two core parts I0 and II and the various windings shown in Fig. 2 are similar to the corresponding arrangements shown in Fig. 1, but the two parts IO'and II of the core are spread apart to show the connections more clearly. Greater compactness is of course secured if the two parts I0 and II of the core are disposed close together with only sufficient space between them to accommodate the windings I3 and i5 as indicated in Fig. i. As.

shown in Fig. 2 the primary winding i2 is com nected in series with one side of an electrical circuit 20 to operate with the secondary winding M as a current transformer supplying current to the ammeter or other instrument Ill. The primary winding 53 is connected across the two sides of the same circuit to to operate with the secondary winding in as a potential transformer connected to the voltmeter to indicate the voltage of the circuit The invention provides a compact and eco nomical transformer which may be used simul= taneously as both a poten .al and a current transformer. It further provides a current transformer extremely high accuracy.

The invention has been explained by describing and illustrating specific arrangements and applications thereof, but will be apparent that changes may be made without departing from the spirit of the invention and the scope of the appended claims.

What claim as new and desire to secure by Letters Patent of the United States isl. A transformer including a magnetic core formed in two parallel parts, primary and secondary current windings on said core parts, and primary and secondary potentiai windings on said. core parts and wound differentially with respect to said current windings.

2. A transformer including a magnetic core formed in two parallel arts, primary and sec-- ondary current windings on "said core parts, and primary and secondary potential windings on said core parts and wound difierentially with respect to said current windings, said primary po tential winding being proportioned to induce magnetic flux at high densityin said core parts.

3. A transformer including a magnetic core aaaaeee formed in two parallel parts, primary and secondary current windings on said core parts, and primary and secondary potential -windings on said core parts and wound differentially with respect to said current windings, said primary potential winding being proportioned to induce magnetic flux in said core parts at a density cor responding substantially to maximum permeability of the core material.

A transformer including a magnetic core formed in two parallel parts, primary and secondary current windings on said core a magnetizing winding on said core and wound iifferent' ly with respect to said cu windings, said pri inagnetiai 1 being connected to the source of. current.

5. A transformer including a magnetic core formed in two parallel parts, primary and sec ondary current ngs on said core parts, and a magnetizing winding on said core parts wound differentially with. respect to said cu windings, said primary magnetizing wi being connected to the same source of c and said magnetizing winding 'peing proportioned to induce magnetic fiua: at high density in said core parts.

6. A transformer including a magnetic core formed in two parallel parts, primary and sec-- o-ndary current windings on said core parts, and a magnetizing winding on said core parts and wound differentially with respect to said cur rent windings, said primary and magnetizing windings being connected to the same source of current, and said magnetizing winding proportioned to induce magnetic flux in said core parts corresponding substantially to maximum permeability of the core material.

GUG-LlELli lZO CAMILLI. 

